California law professor Goodwin Liu, testifies on Capitol Hill in Washington, Friday, April 16, 2010, before the Senate Judiciary Committee hearing on his nomination to be US Circuit Judge for the Ninth Circuit. (AP Photo/Charles Dharapak) (Charles Dharapak - AP)

Senate Republicans mounted a concerted attack Friday on federal appeals court nominee Goodwin Liu in a session that both parties see as a warmup for the coming fight to replace Justice John Paul Stevens on the Supreme Court.

Liu, an associate dean at the University of California at Berkeley law school, is being vetted by the Senate Judiciary Committee for a slot on the U.S. Court of Appeals for the 9th Circuit, which covers nine Western states. Groups on the left strongly support him and many on the right oppose him for the same reason: Liu is an outspoken liberal whose writings have promoted the idea that interpreting the Constitution requires much more than just divining the intent of the Founding Fathers.

In their interrogation of Liu, Senate Republicans are testing arguments they will use when President Obama nominates a successor to Stevens, who has declared his intention to step down from the high court in the coming months. Many Democrats hope Obama will name an outspoken liberal in the mold of Liu, and they plan to mount a vigorous defense of the 9th Circuit nominee to demonstrate that such a candidate can clear the Senate gauntlet.

At the hearing, Republicans attacked Liu on three fronts -- his writings, his experience and his incomplete submission of biographical information to the committee. Jeff Sessions (Ala.), the ranking Republican on the committee, made clear his belief that Liu's writings "represent, I think, the very vanguard of what I would call intellectual judicial activism."

Sessions said Liu would look at the Constitution and "find rights there that have never been found before."

Sen. Orrin G. Hatch (R-Utah) suggested that Liu endorsed allowing judges to disregard the plain meaning of statutes in favor of their personal views. "Do you really think that judges should have this much power over the law?" Hatch asked.

Liu parried Republicans' charges with nuanced answers, saying he found both the "originalist" and "judicial activist" labels insufficiently precise to be useful. Liu said the original intent of the Constitution's framers was "very important" for judges to consider, but "it is not the sole touchstone" of legal interpretation.

Faced with Republicans' citation of several potentially controversial passages in his past writings, Liu made clear that there was a difference between his duties as a law professor and scholar vs. what his responsibilities would be on the bench.

"Whatever I may have written in the books and the articles would have no bearing on my action as a judge," Liu said.

Republicans, particularly Sen. Jon Kyl (Ariz.), were critical of Liu for his past opposition to the Supreme Court nominations of John G. Roberts Jr. and Samuel A. Alito Jr. They focused on a passage from Liu's testimony to the Judiciary Committee during Alito's confirmation, which read: "Judge Alito's record envisions an America where police may shoot and kill an unarmed boy to stop him from running away with a stolen purse; where federal agents may point guns at ordinary citizens during a raid, even after no sign of resistance; . . . where a black man may be sentenced to death by an all-white jury for killing a white man."

"This calls into question your judicial temperament," Kyl said, later adding: "I see it as very vicious and emotionally and racially charged. Very intemperate."

Liu acknowledged using "overly flowery language" but largely stood by his comments. He also compared himself to Alito, noting that both are from immigrant families and have worked their way up from humble origins.

Liu is seen in some quarters as a potential future candidate for the Supreme Court. Liu, the son of Taiwanese immigrants, was a Rhodes scholar and Supreme Court clerk before assuming his current position at Berkeley. No Asian American has served on the Supreme Court, nor are there any Asian Americans among the active judges on the U.S. circuit courts of appeal.

Sen. Dianne Feinstein (D-Calif.), who chaired Friday's hearing and urged Obama to nominate Liu, cited Liu's personal and professional background to make the case for his confirmation in opening remarks at the hearing.

"He has an exceptional legal mind and a deep devotion to excellence in public service," Feinstein said, later adding of the 39-year-old Liu: "I cannot in my time on this committee remember someone quite so young who has done so much."

Republicans had sought to postpone Friday's hearing, with Sessions complaining that Liu omitted several important facts and documents in completing his original questionnaire for the committee.

Liu apologized, calling the omissions innocent mistakes. "My record is an open book," Liu said Friday. "I absolutely have no intention . . . to conceal things that I have said, written or done."

Liu's nomination awaits an as yet unscheduled committee vote before it can proceed to the Senate floor. Democratic leaders hope to move a number of lesser judicial nominations before the fight over Stevens's replacement consumes the chamber's attention, but they have yet to decide which nominees will move when.